“The Man Who Invented Christmas” is a jaunty, amusing patchwork of truths, half-truths and pure fiction that cleverly combine to recount the story of the whirlwind creation of Charles Dickens’ famed novella “A Christmas Carol.” To be clear, the venerated author didn’t exactly “invent” the holiday, but the success of his unique tale did boost the popularity of yuletide and helped launch several of its most celebrated traditions.

The film is anchored by a wonderfully limber and animated title turn by Dan Stevens of “Downton Abbey” fame, and Susan Coyne’s peppy script, based on the book by Les Standiford, mainly covers six pivotal weeks in the hectic life of Dickens in late 1843 London. That was when, apparently fueled by financial and emotional desperation after a post-“Oliver Twist” slump, Dickens miraculously conceived, wrote and self-published what became one of the most beloved — and oft-adapted — yarns of all time.

This is one of the rare movies to make the process of writing feel cinematic (read: exciting), even if it largely relies on fantasy to do so. How Dickens, seen here as a contradictory mix of warm, equitable, impulsive and narcissistic, anxiously concocts what will become “A Christmas Carol” based on the people and the world around him — as well as via a series of dreams and visions — proves enjoyably propulsive.

Sure, some of this can feel contrived. Maybe that’s because we know so well the story Dickens is writing — perhaps even better than he does at this point. But the fun comes not only from being part of Dickens’ artistic method but also from the vivid group of folks we get to meet along the way.

Most notable is a “humbug”-spouting miser (Christopher Plummer, digging in with crusty brio) who will inspire the character of Ebenezer Scrooge, that “Christmas Carol” engine himself.

Then there’s dotty banker-lawyer Haddock (Donald Sumpter), re-imagined by Dickens as Scrooge’s late business partner, Jacob Marley; Dickens’ loyal friend and agent, Forster (Justin Edwards), who is mind-morphed into the Ghost of Christmas Present; the writer’s sister, brother-in-law and sickly young nephew, who will transform into the needy Cratchits; and the Dickens family’s book-loving new chambermaid (Anna Murphy), who’ll come to represent the Ghost of Christmas Past.

The interactions, both real and imagined, with these and other of the novella’s muses, open an entertaining window into Dickens’ increasingly feverish psyche as the days to his publishing deadline tick away.

Tangles with a persnickety book illustrator (Simon Callow) and a prevailing case of writer’s block — or “blockage” at it’s often fustily called here — add to the giddy tension.

Dickens’ personal life also integrally factors in both as thematic inspiration for “Carol” as well as a way to further pile on the pressure: The scribe’s devoted wife, Kate (Morfydd Clark), unexpectedly pregnant with their fifth child, has lost patience with her husband’s writerly self-absorption, while his mother (Ger Ryan) and sincere, if imprudent, father (Jonathan Pryce) pop into town for a distracting visit.

The film darkens and slows a bit in the third act as Dickens mines his poor childhood, including a harrowing stint working in a rat-infested shoe polish factory (talk about Dickensian!) and traumatic events involving his dad, to find “Carol’s” elusive emotional core and eventual message.

Things end on a decidedly upbeat and satisfying note of literary triumph and the kind of familial good cheer in perfect accord with Christmas itself.

Director Bharat Nalluri (“Miss Pettigrew Lives for a Day”), aided immeasurably by his strong production and costume designers, juggles the picture’s many moving parts and cavalcade of performances with skill, ingenuity and a clear affection for his iconic subject.